$\begingroup$Please provide more information, for instance links to relevant protocols that might clarify the origin of the differences. Of the cuff, I'd say solubility though.$\endgroup$
– Night WriterJan 11 at 8:31

1 Answer
1

The flavins are light sensitive and unstable in alkaline solutions. The dry solid is stable to diffuse light, but is highly photolabile in solution, especially in alkaline solutions. Neutral and acidic solutions are stable in the dark (3% decomposition per month at 27 °C at pH 6.0). Acidic solutions may be sterilized by autoclaving.

So making a slightly acidic solution probably helps to prevent decomposition. If you dissolve it in pure water without a buffer, the pH is not well defined.